Both fresh and acetolysed exines of some species (of Lycopodium, Dryopteris, Stylites, and Betula) have been investigated with the polarizing microscope. The following results were obtained: 1. Sporopollenine is isotropic, as far as investigated. 2. The exine does not show any intrinsic birefringence; it contains therefore neither cellulose nor wax in any considerable amount. 3. The exines of all investigated spores and pollen grains show a birefringence of form (textural bir.), due to a very finely layered structure. This indicates, that not only exines, which are found to be layered in the electron microscope (e. g. Lycopodium), but also “amorphous” ones (e.g. Betula) have the character of a layered composite body.